Swiss sensation Roger Federer – a 19-time slam champion – returns to defend his crown at Melbourne Park, starting next week, amid doubts over last year's runner-up Nadal and Djokovic.

Nadal and Djokovic both have fitness concerns following the withdrawal of five-time finalist Andy Murray for the year's opening major, with many tipping an open men's draw.

And Djokovic, who returned to the court midweek amid elbow problems, believes 22-year-old Australian Kyrgios – winner of last week's Brisbane International – can make an impact on home soil.

Asked if Federer and Nadal are the favourites at the Australian Open, Djokovic told Omnisport: "These two guys, considering the year they had and considering they played finals together here in Australia. They're definitely two favourites to look at.

"But it's still open. Nick is in great form. He is a home favourite. Australians are always getting great support here. [Thanasi] Kokkinakis is a good player too.

"Anything can happen. It's a grand slam. Every player is here with all his heart and energy, trying to do his best."

There was a welcome sight for Australian Open organisers and fans when Djokovic made his comeback at the Kooyong Classic on Wednesday, blitzing world number five Dominic Thiem.

A 12-time slam champion and winner of six Australian Open titles, Djokovic was forced to skip the Mubadala World Tennis Championship and the Qatar Open, having not played competitively since withdrawing from the quarter-finals of Wimbledon in July.

But the 30-year-old made light work of Thiem, easing to a 6-1 6-4 victory in the exhibition match in Melbourne.

"Very excited to be back and playing," Djokovic said. "To experience some competitive matchplay. It's not an official tournament but I got to play the number five in the world in Dominic.

"It was a great challenge and test for me. To see where I am, see where my game is at. It's been six months. I missed it a lot. I put a lot of hours into practice sessions. Playing practice sets the last week or so and it paid off.

"I'm still obviously looking forward to improving certain aspects of my game before the Australian Open starts and hopefully I'll be 100 per cent ready."